Wireless communication technologies are widely used in nowadays. FIG. 1A illustrates the schematic view of a conventional wireless communication system 1. The wireless communication system 1 comprises a user equipment 11, a relay station 13, a base station 15, and a core network 17. The user equipment 11 is wirelessly connected to the relay station 13, the relay station 13 is wirelessly connected to the base station 15, and the base station 15 is wiredly connected to the core network 17.
The relay station 13 extends the serving coverage of the core network 17 so that a user equipment that is not in the coverage of the base station 15 but in the coverage of the relay station 13, such as the user equipment 11, can access the service provided by the core network 17. The relay station 13 has the functionalities that the base station 15 has, so the relay station 13 can transmit backhaul control messages to communicate with the core network 17. Conventionally, a backhaul control message is contained within a backhaul transport connection, e.g. Transmission Control Protocol (TCP)/Internet Protocol (IP), User Datagram Protocol (UDP)/Internet Protocol (IP) of the IEEE 802.16m standard, or Stream Control Transmission Protocol (SCTP)/IP of the Long Term Evolution (LTE) standard. It means that the relay station 13 has to create a user plane connection for IP connectivity and transmit or receive a backhaul control message within the user plane connection.
When the wireless communication system 1 conforms to the LTE standard, its protocol stacks are shown FIG. 1B. The protocol stacks 131, 151, and 171 respectively correspond to the relay station 13, the base station 15, and the core network 17. The relay station 13 and the base station 15 communicate with the core network 17 via the S1-AP messages. It can be seen that the S1-AP messages are created upon the SCTP layer and the IP layer.
There are some drawbacks of transmitting a backhaul message in a user plane connection. First, a backhaul control message is a control signal in essential, meaning that a backhaul control message should be treated as having higher priority. Nevertheless, a current relay station transmits a backhaul control message in the low-priority user plane connection, which may cause delay. Second, transmitting a backhaul control message in a user plane requires the creation of an IP layer, which waste radio resources in the wireless link.
If the wireless communication system 1 conforms to the IEEE 802.16m standard, there is no technology addressing on the issue of transmitting a backhaul control message. According to the aforementioned descriptions, a more efficient way to transmit a backhaul control message is needed in the wireless communication field.